Measles, also known as morbilli, English measles, or rubeola (and not to be confused with rubella or roseola) is an infection of the respiratory system caused by a virus, specifically a paramyxovirus of the genus Morbillivirus. Symptoms include fever, cough, runny nose, red eyes and a generalized, maculopapular, erythematous skin rash, the symptom for which measles is best known.
Measles is spread through respiration (contact with fluids from an infected person’s nose and mouth, either directly or through aerosol transmission), and is highly contagious—90% of people without immunity sharing living space with an infected person will catch it. An asymptomatic incubation period occurs nine to twelve days from initial exposure. The period of infectivity has not been definitively established, some saying it lasts from two to four days prior, until two to five days following the onset of the rash (i.e. four to nine days infectivity in total), and whereas others say it lasts from two to four days prior until the complete disappearance of the rash. The rash usually appears between 2-3 days of having Measles.
The classical signs and symptoms of measles include four-day fevers [the 4 D’s] and the three Cs—cough, coryza (head cold), and conjunctivitis (red eyes)—along with fever and rashes. The fever may reach up to 40 °C (104 °F). Koplik’s spots seen inside the mouth are pathognomonic (diagnostic) for measles, but are not often seen, even in real cases of measles, because they are transient and may disappear within a day of arising.
Measles is caused by the measles virus, a single-stranded, negative-sense, enveloped RNA virus of the genus Morbillivirus within the family Paramyxoviridae. Humans are the natural hosts of the virus; no other animal reservoirs are known to exist. This highly contagious virus is spread by coughing and sneezing via close personal contact or direct contact with secretions.
Risk factors for measles virus infection include; Travel to areas where measles is endemic or contact with travelers to endemic areas, Infants who lose passive antibody before the age of routine immunization.
Clinical diagnosis of measles requires a history of fever of at least three days, with at least one of the three C’s (cough, coryza, conjunctivitis). Observation of Koplik’s spots is also diagnostic of measles. Alternatively, laboratory diagnosis of measles can be done with confirmation of positive measles IgM antibodies or isolation of measles virus RNA from respiratory specimens. In patients where phlebotomy is not possible, saliva can be collected for salivary measles-specific IgA testing. Positive contact with other patients known to have measles adds strong epidemiological evidence to the diagnosis. The contact with any infected person in any way, including semen through sex, saliva, or mucus, can cause infection.
In developed countries, children are immunized against measles by the age of 18 months, generally as part of a three-part MMR vaccine (measles, mumps, and rubella). The vaccination is generally not given earlier than this because sufficient antimeasles immunoglobulins (antibodies) are acquired via the placenta from the mother during pregnancy may persist to prevent the vaccine viruses from being effective. A second dose is usually given to children between the ages of four and five, to increase rates of immunity. Vaccination rates have been high enough to make measles relatively uncommon. Even a single case in a college dormitory or similar setting is often met with a local vaccination program, in case any of the people exposed are not already immune. Adverse reactions to vaccination are rare, with fever and pain at the injection site being the most common. Lives threatening adverse reactions occur in less than one per million vaccinations.
There is no specific treatment for measles. Most patients with uncomplicated measles will recover with rest and supportive treatment. It is, however, important to seek medical advice if the patient becomes more unwell, as they may be developing complications.
Some patients will develop pneumonia as a sequelae to the measles. Other complications include ear infections, bronchitis, and encephalitis. Acute measles encephalitis has a mortality rate of 15%. While there is no specific treatment for measles encephalitis, antibiotics are required for bacterial pneumonia, sinusitis, and bronchitis that can follow measles.